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EECS – Prof. A. Casalegno – 24th January 2020 1 Basic Part (3 points per questions, minimum score 12) 1. Write the Nernstian equilibrium potentials for both electrodes of a PEM fuel cell as a function of chemical activities 2. Write the Nernst-Plank equation for mass transport in a solid electrolyte 3. Define the efficiency for a battery following a complex operation profile 4. Write Faraday’s law applied to reactants in a PEM electrolyser Name _____________________________ Person N. __________________________ EECS – Prof. A. Casalegno – 24th January 2020 2 Exercise 1 A PEM electrolyser stack consumes at full load 400 A at 360 V with an efficiency equal to 67.5% (LHV=120 MJ/kg). Assuming that 2% of H2 is wasted and its performance follows the reported polarization curve, estimate the number of cell, cell area and efficiency at 20% current load. Exercise 2 A Li-ion battery with nominal capacity of 50 Ah operates at ambient pressure and temperature, supplying 3.6 V during discharge at SoC=90% and C-rate=3. Assuming that: 1. Tafel kinetics is valid for both electrodes 2. ion and mass transport effects in electrodes are negligible 3. activities of reactants in discharge are close to the value of SoC 4. electrolyte resistance is equal to 2 mΩ 5. transfer coefficients of both electrodes during discharge are equal to 0.5 Discharging at C-rate=4, the voltage reaches the value 3.3 V, estimate the achieved SoC. ∆𝑉 0 𝑗 1.45 V 1.8 V 0.4 A cm-2 2 A cm-2 EECS – Prof. A. Casalegno – 24th January 2020 3 Intermediate Part (2.5 points per questions) 1. Is the overpotential positive when H2 oxidation occurs? Demonstrate analyzing 𝐺% 2. Show how voltage limits could reduce the available capacity at high C-rate in batteries 3. Depict the polarization curves of 3 different PEMFC: 1) ECSA=60…